372 Boltwood — Note on a New Radio- Active Element. 



actinium X can be observed, but if actinium were present a 

 separation of this product would be expected. 



The most conclusive proof that the substance described is 

 a new radio-active element is furnished by the properties of 

 its a-radiation. The a-rays which it emits are much more 

 readily absorbed by aluminium than the a-rays from polonium, 

 with which it has been directly compared. Their range 

 in air as determined by the scintillation method appears 

 to be less than 3 centimeters, which is less than the range of 

 the a-particle from any other known radio-active element. The 

 new substance also gives out a /3-radiation which is less pene- 

 trating and more easily absorbed than that from uranium, the 

 value found for the coefficient of absorption being about 1*8 

 aluminium. 



Experiments which have been carried out with a view to 

 obtaining a quantitative separation of this new element from 

 small quantities of very pure uraninite have given results which 

 are in good agreement with one another and which indicate 

 that the activity of the new element in equilibrium with radium 

 is about OS of the activity of the radium itself with which it is 

 associated. This is about the value to be expected if the new 

 substance is intermediate between uranium and radium when 

 the range of a-particles in air is taken into consideration. It 

 is very likely that this radio-active element is present in Debier- 

 ne's actinium preparations and in some of Giesel's "emaniurn" 

 compounds which have been put on the market by the Chinin- 

 fabrik, Braunschweig, especially in the former, and its presence 

 may perhaps explain the confusion which has resulted from 

 Debierne's earlier assertions that actinium accompanied thorium 

 as opposed to Giesel's positive statements to the contrary.* 



. Strong evidence has, therefore, been obtained of the existence 

 in uranium minerals of a new radio-active element, which emits 

 both a and /3 radiations, which produces no emanation and 

 which resembles thorium in its chemical properties. It is with- 

 out doubt a disintegration product of uranium and is in all prob- 

 ability the immediate parent of radium. The name "Ionium" 

 is proposed for this new substance, a name derived from the 

 word "ion". This name is believed to be appropriate because 

 of the ionizing action which it possesses in common with the 

 other elements which emit a-radiations. 



Further experiments are in progress which it is hoped will 

 afford additional information as to the properties and chemical 

 behavior of this new body. 



Sloane Laboratory, Yale University, 



New Haven, Conn., Sept. 21, 1907. 



*Chem. Berichte, xl, 3011, 1907. 



